In a traditional cable TV set-top box design, both a front-end circuit and a back-end circuit are controlled by a single central processor. Control of a tuner and a demodulator by the processor is achieved by direct register access via a parallel or a serial bus. Technology evolved such that the front-end circuit became very complicated. One central processor is not capable of simultaneously controlling front-end circuits for Data Over Cable Service Interface Specification (DOCSIS) communication and back-end circuits for cable TV functions.
Thus, a conventional set-top box was designed that provides DOCSIS service with a DOCSIS-dedicated processor connected to a single DOCSIS-dedicated tuner and a single DOCSIS-dedicated demodulator. The conventional set-top box provides CATV service with a CATV-dedicated processor connected to a separate, CATV-dedicated tuner and a separate, CATV-dedicated demodulator. Thus, in the conventional set-top box, circuits providing both DOCSIS and CATV services do not share tuners and demodulators. Further, in a conventional set-top box providing both DOCSIS and CATV service, DOCSIS and CATV processors do not share control of tuners and demodulators, nor do the DOCSIS and CATV processors communicate with each other to share control of their respective tuners and demodulators.
Thus, what is needed is a control circuit configuration and communication protocol that are capable of simultaneously controlling the DOCSIS front-end and the back-end circuit as well as overcome other shortcomings stated above.